The bottomless bag, is a very old trick well known to professional thieves operating at airports and railways station in Europe.
Another popular trick is just to pick up a black piece of luggage from the carousel.
After all they all look the same or so you can claim, if you get caught…

It's one of many reasons why I travel with just a day pack — like this one or this one — on my person. My pack is never much more than half full — and it carries everything I need to travel for months and months — from freezing to tropical climes.

The booster bag is cool, and sinister. I've seen video where a team were using versions large enough to fit over full, hard-side suitcases at the airport sidewalk. I tend to carry things I really can't do without, or let others have, and usually sit with my hand literally on my bag(s) or those of my traveling companions.